effects of formalin as a peripheral noxious stimulus on the nucleus reticularis paragigantocellularis neurons of anesthetized rats

in the present study, the effects of formalin as a peripheral noxious stimulus on spontaneously active units of the nucleus reticularis paragigantocellularis (pgi), a narrow region of the ventral pontine reticular formation, was examined in urethane anesthetized rats. spontaneous discharge of the pgi neurons was variable, ranging from i to 37 spikes per second. formalin as a chemical irritant and prolonged noxious stimulus induced changes in the firing of spontaneously active pgi neurons. there were three neuronal subpopulations in the pgi that responded to formalin: excited (19.35 %), inhibited (45.16 %) and unchanged (35.48 %). thus we suggest that pgi neurons may be involved in the processing of information related to formalin as a chemical irritant.